At 20:19 -0500 03/18/2002, Tom & Lisa P wrote: >>What I've ended up with is: >> >>Motherboard: S900 (perhaps with a bad SCSI Bus 0)--will probably > >Interesting. I have a J700 with the same problem. I wonder if there >is a fuse solely for SCSI bus 0.
I don't think there is a fuse, but SCSI bus 0 is controlled by the MESH chip--a 100 pin Apple chip with 30 pins on the long side and 20 down the short side. SCSI bus 1 is controlled by the CURIO chip which is an AMD chip Apple has used at least all the way back to the NuBus Power Macs. So one could have a problem in the MESH chip (bus 0) and not affect the CURIO chip (bus 1). There are also assorted chips to provide the termination power (a Voltage Regulator especially for SCSI termination power) and the termination resistors. Seperate chips for each bus. However, in my case I also tried inserting an internal pass-through 50 pin terminator where the ribbon cable meets the motherboard, thinking that would solve the problem if it was termination related. But it didn't help. Now, it could still be related to term. power, so I need to try again with a device on the chain which can supply termination power. Neither the 4416, nor the Plextor 20X have a jumper for term. power. So many tests, so little time. If it boils down to the MESH chip, that's a tough one. I think I have a couple of dead x500 boards I can steal a MESH chip from, so that'll probably work out okay. On the PM 8100, Apple used the NCR 53CF96 for the Fast SCSI bus, which was in exactly the same 100 pin package. I half way suspect that the MESH chip is just Apple's licensed version of the NCR chip and it would be interesting to see what happens if one installs the NCR chip. A few years ago I picked up four of the 53CF96s with which to fix an 8100 board. It was tough because NCR's semiconductor division no longer exists. I eventually figured out that SymBIOS bought the division and then LSI Logic bought SymBIOS, so the chips were actually LSI chips when I got them. However, they were at End Of Life at the time, so I doubt that they are still in production. >>Hard Drives: Three LVD 18 GB Western Digital drives in striped RAID >>on 2940UW. I lose some performance as the three drives outperform >>the 2940UW. Hence the need for a U2W card. One 40 GB IBM 75GXP on >>the VST card. > >Is MacGurus out of the U2B cards ? I believe so, since they aren't on their web page any more. If you really need to know I can email Magician. The U2B won't work for me because it seems to be incompatible with the VST card. So, since I'm going to need a new U2W card anyway, I may as well get the Miles2 because it is reputed to be the best of the U2W cards. If there are other opinions on that I'm happy to hear them. I haven't tested the various options. Jeff Walther -- SuperMacs is sponsored by <http://lowendmac.com/> and... Small Dog Electronics http://www.smalldog.com | Refurbished Drives | Service & Replacement Parts [EMAIL PROTECTED] | & CDRWs on Sale! | PowerON Computer Services <http://www.poweron.com> REPLACEMENT PARTS in STOCK Drives, CD-ROMs, RAM, Processors, Power Supply <mailto:[EMAIL PROTECTED]> Support Low End Mac <http://lowendmac.com/lists/support.html> SuperMacs list info: <http://lowendmac.com/supermacs/list.shtml> Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/supermacs%40mail.maclaunch.com/> Using a Mac? Free email & more at Applelinks! http://www.applelinks.com
